The invention relates to the field of silicon micromachined devices and in particular mems pumps.
The invention is an apparatus which is comprised of a micromachined substrate having an orifice defined therethrough, and a micromachined elastic valve structure disposed over the orifice and coupled to the substrate. The valve structure and substrate act in combination as a passive check valve for the flow of fluid through the orifice. Silicon micromachined elements are contemplated, but micromachining of other materials can also be practiced. The term silicon micromachining therefore need not involve the machining of silicon or a semiconductor, but generally refers to mems or microelectromachining techniques.
The apparatus further comprises a housing in which the micromachined substrate and micromachined elastic valve structure are disposed. The housing defines a pumping chamber with which the check valve is communicated. In an operating pump there are two check valves disposed within the housing. One of the two check valves is communicated with the pumping chamber to allow flow to the pumping chamber and the other of the two check valves is communicated with the pumping chamber to allow flow from the pumping chamber. An elastic membrane is communicated with the pumping chamber to transmit pressure variations into the chamber to activate the check valve(s). A plunger is directly or fluidically indirectly coupled to the elastic membrane to transmit force to the elastic membrane to create the pressure variations into the chamber to activate the check valve(s). An actuator is coupled to the plunger to move the plunger thereby ultimately causing the pressure variations into the chamber to activate the check valve so that in combination a pump is provided.
In the illustrated embodiment the micromachined elastic valve structure is comprised of Parylene C and the elastic membrane is comprised of silicone rubber. The micromachined elastic valve structure is comprised of an integral elastic layer in which a valve cap and a plurality of extendable tethers are defined. The valve cap is positioned and sized to seal the orifice defined through the substrate when the valve cap is passively forced by fluid pressure toward the orifice, and to open the orifice when the valve cap is passively forced by fluid pressure away from the orifice. While in the illustrated embodiment, passive valve elements are contemplated it is within the scope of the invention that the valve elements may be active, namely may have disposed in or on them devices which cause the valve elements themselves to move toward or away from the orifice, such as electromagnetic or electrostaticly driven microactuators.
The housing is micromachined, but may include portions which are conventionally machined in combination with the micromachined check valve(s). In the illustrated embodiment the housing comprises a valve support and a spacer between which the micromachined elastic valve structure is disposed. The detailed design of the housing may be varied in both form and substance in a wide variety of ways while still providing the same functional results of supporting the check valve(s) in relation to a pumping chamber and inlet/outlet orifices.
The invention is also a method comprising the steps of defining a support membrane and underlying chamber in a substrate. A first patterned elastic layer is disposed on the substrate. A sacrificial layer is disposed over the support membrane. A second patterned elastic layer is disposed on the sacrificial layer and on the first patterned elastic layer. The support membrane and sacrificial layer is removed to release the first and second patterned elastic layer and to define an orifice through the substrate in communication with the chamber. As a result, a structure is formed in which the first and second patterned elastic layer function as a passive check valve for fluid flow through the orifice.
The method further comprises providing a diaphragm and coupling the diaphragm to the substrate so that the diaphragm forms at least a portion of a wall defining the chamber. A housing is provided in which the check valve is disposed and which defines an inlet/outlet orifice through the housing communicating through the check valve with the chamber. A plunger is coupled to the diaphragm and an actuator coupled to the plunger wherein the diaphragm is moved to create pressure variations within the chamber. Providing two opposing directed check valves results in a pump, while a single check valve is usable as a microhydraulic actuator.
The illustrated embodiment of the invention having now been briefly summarized turn to the following drawings where one embodiment of the invention can be visualized and where like elements are reference by like numerals.